US3892156A

US3892156A - Knife holders for slitter winding machines and the like

Info

Publication number: US3892156A
Application number: US441207A
Authority: US
Inventors: Bruce V Johnstone
Original assignee: Johnstone Eng & Mach Co
Current assignee: Johnstone Eng & Mach Co; Johnstone Engineering & Machine Co
Priority date: 1974-02-11
Filing date: 1974-02-11
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01
Also published as: DE2451491A1

Abstract

A pressure fluid operated knife holder comprising a cylinder having a piston and piston rod therein, and a knife head carried by the piston rod. The piston, piston rod and knife head assembly are fluid pressure actuated from an upper limit position to a lower limit position in which a male knife on the head is positioned relative to a female knife. Adjustable means is provided for initially setting the cutting edge of the male knife relative to the female knife in the lower limit position of the assembly. The male knife is supported by a mounting axially movable in the knife head between inner and outer positions to set the male knife in cutting position against the female knife, and the mounting also has limited rocking movement to equalize contact pressure between the male and female knives. Outward axial displacement of the mounting to set the male knife is accomplished by pressure fluid from the cylinder and the connections from the cylinder to the knife head are constructed and arranged so that pressure fluid cannot flow from the cylinder to the knife head until the assembly is in the lower limit position. Pressure fluid admitted to the knife head is vented to atmosphere in all positions of the assembly except said lower limit position.

Description

" United States Patent 91 J ohnstone 1 July 1,1975

[ KNIFE HOLDERS FOR SLITTER WINDING MACHINES AND THE LIKE [75] Inventor: Bruce V. Johnstone, Gap, Pa.

[73] Assignee: Johnstone Engineering & Machine Company, Parkesburg, Pa.

221 Filed: Feb.ll, 1974 211 App1.No.:441,207

[52] U.S. Cl. 83/469; 83/482; 83/501; 83/5081, 83/562 [51] Int. Cl. B23D 19/00; 826D H14 [58] Field of Search 83/482,501, 502, 503, 83/562, 508.2, 469

[56] References Cited UNITED STATES PATENTS 3,186,281 6/l965 Wingen 83/501 X 3,380,330 4/1968 Gilmore 83/503 X Primary Examiner-Willie G. Abercrombie Attorney, Agent, or FirmHowson and Howson [57] ABSTRACT A pressure fluid operated knife holder comprising a cylinder having a piston and piston rod therein; and a knife head carried by the piston rod. The piston, piston rod and knife head assembly are fluid pressure actuated from an upper limit position to a lower limit position in which a male knife on the head is positioned relative to a female knife. Adjustable means is provided for initially setting the cutting edge of the male knife relative to the female knife in the lower limit position of the assembly. The male knife is supported by a mounting axially movable in the knife head between inner and outer positions to set the male knife in cutting position against the female knife. and the mounting also has limited rocking movement to equalize contact pressure between the male and female knives. Outward axial displacement of the mounting to set the male knife is accomplished by pressure fluid from the cylinder and the connections from the cylinder to the knife head are constructed and arranged so that pressure fluid cannot flow from the cylinder to the knife head until the assembly is in the lower limit position. Pressure fluid admitted to the knife head is vented to atmosphere in all positions of the assembly except said lower limit position.

21 Claims, 8 Drawing Figures KNIFE HOLDERS FOR SLI'I'TER WINDING MACHINES AND THE LIKE This invention relates to new and useful improvements in knife holders for slitter winding machines and the like. More particularly, the invention relates to knife holders of the fluid pressure actuated type having separate means for lowering the knife relative to the material to be cut and for laterally setting the knife relative to the cooperating mating knife of the machine.

Prior knife holders of the type described are characterized by certain objectionable features and disadvantages. For example, in some prior knife holders it frequently occurs that the lateral set or shift of the male knife relative to the female knife of the machine will commence or take place before the male knife has reached the full lowered position thereof in proper overlapping relation to the female knife of the machine thereby causing premature engagement of the knives with resulting damage to the male knife. Also, the construction and arrangement of some prior holders is such that when cutting heavy weight dense board with taped lapped splices sufficient resistance may be presented to elevate the male knife when it is laterally set or shifted and the male knife will engage and ride on the surface of the female knife as in a score type cut with resulting damage to the male blade.

Another objection to prior knife holders of the aforesaid type is that the construction and arrangement for mounting the male knife member causes variations in the contact pressure between the male and female blades resulting in excessive wear of the blades. Also, in a number of prior devices it is difficult to remove and replace the male knife on the knife holder.

With the foregoing in mind, an object of the present invention is to provide a novel knife holder of the type described that is constructed and arranged to prevent lateral setting or shifting of the male knife until the latter has attained its fully lowered position in proper overlapping relation to the female knife of the machine.

Another object of the invention is to provide a knife holder of novel construction in which any tendency for the male knife to override the female knife of the machine is prevented.

Another object of the present invention is to provide a knife holder having the features and advantages set forth wherein the contact pressure between the male and female knives is substantially constant at all times.

A further object of the invention is to provide a novel knife holder construction in which removal and replacement of the male knife may be readily and easily accomplished.

These and other objects of the invention and the various features and details of the construction and operation thereof and hereinafter fully set forth and described with relation to the accompanying drawings, in which:

FIG. I is a side elevational view partially in section of a knife holder embodying the present invention showing the male knife actuating piston in the raised inoperative position;

FIG. 2 is a front clevational view of the knife holder shown in FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view on line 33, FIG. 2;

FIG. 4 is a fragmentary sectional view of the upper portion of FIG. 3 showing the male knife actuating piston and associated parts in the fully lowered operative position of the male knife;

FIG. 5 is a fragmentary sectional view on line 5-5, FIG. 3;

FIG. 6 is an enlarged partial sectional view on line 6-6, FIG. 1;

FIG. 7 is a view similar to FIG. 6 showing the male knife and its supporting head in the fully lowered cutting position; and

FIG. 8 is a sectional view in reduced scale on line 8-8, FIG. 6.

Referring now to the drawings, FIGS. 1-3 thereof, show one embodiment of the present invention comprising a vertically disposed cylinder 1 having an integral bracket portion 2 projecting laterally therefrom constructed and arranged for slidable mounting on the arbor 3 of a typical slitter winding machine. The bracket 2 is fixedly secured to the arbor 3 by means of a Reid screw 4. The arbor 3 extends horizontally crosswise of the slitter winder machine, and customarily a plurality of knife holders is mounted on the arbor 3 at spaced intervals therealong according to the widths of the strips into which the web material is to be cut. The individual knife holders may be adjustably positioned and secured as desired along the arbor 3 by loosening the Reid screw 4, grasping the handle 5 and then retightening the Reid screw 4.

Referring more particularly to FIG. 3, the cylinder 1 has upper and lower annular end members 6 and 7, respectively, fixedly secured in place by means of snap rings 8 and 9. The upper annular end member 6 is provided with an annular packing ring 10 seated in an annular groove 11 formed in the outer surface of the member 6 and disposed in sealing engagement with the adjacent inner wall surface of the cylinder I. Lining the interior wall of the cylinder 1 between the cylinder end members 6 and 7 is a tubular cylindrical sleeve 12 in which is slidably mounted an annular piston 13 of comparatively short axial length. The piston 13 is provided with piston ring 14 seated in a groove 15 and the ring 14 has sliding sealing engagement with the inner wall surface of the cylinder sleeve 12.

The annular piston 13 is mounted on a piston rod 16 that extends coaxially within the cylinder 1 and lining sleeve 12. The piston rod 16 comprises an intermediate portion 17 that extends through the annular piston 13 and has an external diameter substantially the same as the internal diameter of the piston. A lower portion 18 of the piston rod 16 has a larger diameter than the piston portion 17 and provides an annular shoulder 19 on which the piston 13 is seated and firmly secured on the piston rod 16 by a snap ring 20. An O-ring type seal 21 is mounted in the portion 17 of the rod 16 adjacent the annular shoulder 19.

The piston rod 16 also comprises an upper portion 23 having a diameter less than the intermediate portion I7 and a terminal end portion 24 of less diameter than said portion 23. The rod portion 23 is externally threaded as shown and threaded thereon is the internally threaded annular skirt portion 25 of an adjustment thimble 26 that also has a recess 25a of smaller diameter to receive the terminal end portion 24 of the piston rod 16. The purpose and operation of the adjustment thimble 26 is hereinafter set forth. The adjustment thimble 26 extends coaxially through the annular cylinder end member 6 and is rotatably adjustable axially on the piston rod 16. A fluid pressure tight seal is provided between the adjustment thimble 26 and the cylinder end member 6 by a packing ring 27 recessed in the inner wall surface of said member 6. and a further seal between the end member 6 and thimble 26 is provided by an O-ring 28 seated in a recess 29 in the upper end face of the member 6 and circumscribing the external surface of the adjustment thimble 26.

An expansion spring 30 is coiled about the lower portion 18 of the piston rod l6 and acts between the lower cylinder end member 7 and the piston 13 normally to urge said piston 13 and piston rod 16 upwardly to the elevated or inoperative position of the knife holder shown in FIGS. 1-3 of the drawings. In the illustrated embodiment of the invention the piston 13 and piston rod 16 are actuated downwardly within the sleeve 12 of cylinder l against the expansion force of the spring 30 by means of air under pressure admitted to the cyl inder 1 above the piston 13 through a suitable fitting 31.

As will be apparent from FIGS. 3 and 4 of the drawings. axial movement of the piston rod 16 in either di rection is accompanied by a corresponding axial move ment of the adjustment thimble 26 relative to the annular cylinder end member 6. The upper limit position of the piston assembly. comprising piston 13. piston rod 16 and adjustment thimble 26, is fixedly determined by a snap ring 32 that is seated in a groove 33 formed in the outer surface of the skirt portion 25 of the thimble 26 and engages against the undersurface of the annular cylinder end member 6 as shown in FIG. 3. The adjustment thimble 26 is provided with an enlarged head portion 34 and the lower limit position of the piston assembly is fixedly determined by engagement of the undersurface 35 of the thimble head portion 34 with the adja cent surface of the cylinder end member 6 as shown in FIG. 4 of the drawings. By this construction and arrangement the stroke of the piston. rod and thimble assembly is constant and equal to the axial distance between the snap ring 32 and the undersurface 35 of the thimble head portion 34.

Referring to FIGS. 3, 6 and 7 of the drawings. the portion 18 of the piston rod 16 extends slidably through the annular member 7 at the lower end of the cylinder 1 and terminates at short distance therebelow. The piston rod 16 normally is secured against rotation relative to the annular end member 7 by means of a key 36 mounted in confronting

keyways

37 and 38 provided, respectively. in the piston rod portion 18 and end mem ber 7, for example. as shown in FIG. 5 of the drawings. The key member 36 is secured in place by suitable fastening means such as a screw 39 and the annular end member 7 is fixedly secured rotationally with respect to the cylinder 1 by means of a set screw 40.

Secured to the lower end of the piston rod portion 18, for example by welding 41, is a supporting head 42 for the male knife of the knife holder. The head 42 is of cylindrical construction having an axial recess 43 of relatively large diameter defined by a cylindrical internal wall surface 44 and an axial recess 45 of smaller diameter defined by the cylindrical internal wall surface 46. The larger recess 43 is partially closed by an annular end ring 47 secured in place. for example. by screws 48 and the recess 45 is closed by an end plate 49 secured in place. for example by screws 50.

Mounted axially in the head 42 for limited axial and rocking movement therein is a bearing support. generally designated 51. comprising an annular member 52 disposed in the recess 43 and a member 53, secured to the member 52 by screws 54, that projects axially within the recess 45 and has an external diameter somewhat less than the diameter of the wall 46 of said recess 45.

The peripheral surface 55 of the bearing support member 52 engages with the circumscribing cylindrical wall surface 44 of the recess 43 and is provided with an arcuate spherical surface contour as shown in FIGS. 6 and 7 having a radius described from the center 0 located on the axis of the knife head 42.

The member 52 of the bearing support 51 includes an axially extending annular sleeve portion 56 that projects endwise through the central opening in the end ring 47 of the head 42, and the stub shaft 57 of a knife mounting plate 58 is rotationally mounted in said sleeve 56. for example. by means of a bearing assembly 59. A male cutting knife 60 is frictionally secured with respect to the plate 58, for example. by means of a beveled snap ring 62 engaged in a suitable slot 63 in the mounting plate 58. The bearing assembly is secured in the sleeve 56, for example. by means of a snap ring 64 engaged in an internal groove 65 of said sleeve.

Sufficient clearance is provided between the support member 52 and the end ring 47 of the head 42 to permit limited axial movement of the support 51 within the head 42 and. of course. any such axial movement of the support 52 is accompanied by a corresponding axial movement of the mounting plate 58 and knife 60 carried thereby. Also. limited rocking movement of the bearing support 51 about the center c within the head 42 is afforded by the arcuate spherical peripheral surface 55 on the member 52.

When the male knife 60 is inoperative. the mounting 51 normally is maintained in the axial inward limit position thereof shown in FIG. 6. by means of a plurality of expansion coil springs 66 arranged in equally spaced circumferential relation (see FIG. 8) and mounted in counterbored recesses 67 in the member 52. The springs 66 react between the inner surface of the end ring 47 and annular shoulders 68 at the inner ends of the recesses 67. and smaller diameter passage 69 extend from each recess 67 entirely through the member 52 to vent any pressure build-up between the member 52 and head 42 that might tend to oppose actuation of the mounting 51 to the inward limit position by the springs 66.

Actuation of the mounting 51 and knife 60 axially outward relative to the head 42 to the operative position shown in FIG. 7 of the drawings is accomplished by fluid pressure. such as air. admitted to the head recess 45 and acting upon a flexible diaphragm 70 constructed and arranged as shown more particularly in FIGS. 6 and 7 of the drawings. The central circular portion 71 of the diaphragm 70 is adhesively secured to the adjacent surface of the bearing support member 53 and the peripheral edge portion 72 of said diaphragm 70 is fixedly secured in an annular groove or recess 73 provided as shown in the head member 42. The diaphragm 70 also includes an annular bellows type reversely folded portion 73 surrounding the member 53 and interposed between the latter and the adjacent circumscribing wall surface 46 of the head member 42.

Pressure fluid is supplied to the recess 45 of the head 42 through a radial passage 74 formed in the closure plate 49 and terminating at its outer end in an axial port 75 disposed in confronting communication with an axial passage 76 formed in the head member 42 and communicating at its inner end with a radial passage 77. At its outer end the passage 77 in the head member 42 is in open communication with a coaxial recess 78 provided in the lower end of the portion 18 of the piston rod 16, and communicating with said recess 78 is a passage 79 that extends coaxially within the piston rod 16 for the entire length thereof as shown in FIG. 3 of the drawings, the upper end of the passage 79 at the tip of the terminal end portion 24 of the piston rod 16 is in open communication with the recess 25a of the adjustment thimble 26.

As previously stated, a particular feature of the present invention is the provision of a knife holder construction of the type described in which lateral setting of the knife is positively prevented and cannot occur until the knife has been actuated to its fully lowered position in proper overlapping relation with the cooperating female knife of the machine. According to the invention this is accomplished by constructing and arranging the inlet port for the flow of pressure fluid from the cylinder 1 to the diaphragm chamber 45 so that said port is opened to receive pressure fluid from the cylinder I only when the piston 13, rod 16 and knife head 42 have been actuated to the lower limit position. Provision is also made to vent the diaphragm chamber 45 to atmosphere at all times except in the lower limit position of the piston assembly.

In the illustrated embodiment of the invention, a radial port 80 to receive pressure fluid from the cylinder 1 is provided in the external wall of the adjustment thimble 26 and is spaced vertically below the undersurface 35 of the thimble head 34 a predetermined distance slightly greater than the thickness of the cylinder end member 6. By this construction and arrangement it will be apparent that the port 80 is open to the interior of the cylinder 1 to receive pressure fluid only in the lower limit position of the piston, rod and thimble assembly determined by the under surface 35 of the thimble head 34, as shown in FIG. 4 of the drawings.

The radial port 80 at the inner end thereof communicates with a vertical passage 81 in the wall of the thimble 26 and this passage 8] communicates at its upper end with a radial passage 82. The radial passage 82 extends entirely through the thimble wall immediately below the head 34 of the thimble 26 and provides a vent for pressure fluid from the thimble chamber 25:: to the ambient atmosphere except in the lower limit position of the thimble in which the outer end of the vent passage 82 is closed by the seal 28 in the cylinder end member 6 as shown in FIG. 4.

By virtue of the construction and arrangement shown and described, pressure fluid admitted to the cylinder 1 through fitting 31 cannot enter the port 80 and flow through the connecting passages and ports to the diaphragm actuating chamber 45 in the head 42 until after the pressure fluid in the cylinder has actuated the piston rod and thimble assembly to the lower limit position thereof shown in FIG. 4 of the drawings. In the upper limit position of said assembly shown in FIG. 3, and in all intermediate positions thereof. the port 80 is closed to communication with the cylinder 1 and the vent passage 82 is open to the ambient atmosphere.

Thus, at the end of a slitting operation during which the piston knife head assembly is in the lower limit position upon cut-off of the pressure fluid supply to the cylinder 1, the spring 30 in the cylinder I will actuate the piston-knife-head assembly to the upper limit position shown in FIG. 3. At the start of upward movement of the piston-knife-head assembly the vent port 82 will be opened to atmosphere and pressure fluid in the diaphragm actuating system will immediately be vented to the atmosphere so that the springs 66 immediately return the knife 60 and mounting 51 axially to the inner limit position thereof as shown in FIG. 6.

In operation of a knife holder embodying the present invention it is essential that all such devices in the slitter-winding machine be initially adjusted to bring the edge of the male knife 60 of each holder into proper overlapping relation with respect to its cooperating fe male knife 83. In the illustrated embodiment of the invention this is accomplished by manually exerting downward pressure on the thimble head 34 and actuating the piston-knife head assembly to the lower limit position thereof previously described. While held in the lower limit position, the thimble 26 is rotated either clockwise or counter-clockwise as may be required, for example, be means of a spanner wrench engaged in one of the recesses 340 provided in the lateral peripheral surface of the thimble head 34.

Rotation of the adjustment thimble 26 as described operates to effect vertical adjustment of the piston 13 and piston rod 16 coaxially within the cylinder 1 and a corresponding vertical adjustment of the knife head 42 and knife 60 relative to the cooperating female knife 83. Normally, it is desirable that in the lower limit position of the knife 60 the cutting edge thereof overlaps the circumference of the female knife 83 a predetermined distance, for example, about 1/6 inch, as shown in dotted lines in FIG. 6 of the drawings. This adjustment may just be made separately for each knife holder in the machine since the radius of the knife in each holder will vary from holder to holder due to frequent resharpening and periodic replacement of the male knifes 60 as the result of wear.

After the male knives 60 of all of the knife holders in the machine have been adjusted and set as described, the machine is placed in operation and pressure fluid such as air is admitted through fitting 31 to the cylinder 1 thereby actuating the piston-knife head assembly to the lower limit position shown in FIG. 4 wherein the cutting edge of the blade 60 is disposed in the dotted line position shown in FIG. 6. As the piston-knife head assembly reaches its lower limit position the port 80 is opened and pressure fluid in the cylinder 1 flows through the connecting passages and ports to the chamber 45 in the knife head 42 thereby actuating the flexible diaphragm to cause axial displacement of the mounting 51, plate 58 and male knife 60 from the inoperative position shown in FIG. 6 of the drawings to the operative position thereof shown in FIG. 7, in which the cutting edge of the male knife 60 is brought into cutting engagement with the web material w and the cooperating female knife 83.

Engagement of the cutting edge of the male knife 60 with the cooperating female knife 83 causes a slight angular deflection of the male knife 60 from the horizontal axis x to the axis y as shown in FIG. 7 causing a corresponding rocking movement of the mounting 51 relative to the knife head 42 as shown in FIG. 7 of the drawings. This rocking movement of the mounting 51 eliminates variations in the contact pressure between the male and female knives so that the contact pressure therebetween is substantially constant at all times.

Upon completion of the slitting and winding operation of the machine the supply of pressure fluid to the cylinder 1 is cut off thereby permitting the spring 30 to move the piston-knife head assembly toward and to the upper limit position thereof and immediately vent pressure fluid in the diaphragm actuating chamber through the vent passage 82 in the adjustment thimble 26, thereby causing the springs 66 immediately to return the mounting 51, plate 58 and male knife 60 axially inwardly of the head 42 to the position shown in FIG. 6 of the drawings.

From the foregoing it will be apparent that the present invention provides a knife holder of novel construction and arrangement in which lateral setting or shifting of the male knife is prevented and cannot take place until said male knife has attained its fully lowered position in proper overlapping relation to the female knife of the machine. The invention also provides a knife holder of novel construction and arrangement wherein the contact pressure between the male and female knives is substantially constant at all times and in which any tendency for the male knife to override the female knife is eliminated. The invention also provides a construction in which the removal and replacement of the male knife may be readily and easily accomplished.

While a particular embodiment of the invention has been illustrated and described, it is not intended to limit the invention to such disclosure and changes and modifications may be made therein and thereto within the scope of the appended claims.

I claim:

I. A pressure fluid actuated knife holder comprising a cylinder, a=piston rod extending axially through said cylinder beyond the ends thereof and having a pressure fluid passage extending coaxially therein, a piston in the cylinder secured on said piston rod, intercooperating means on the piston rod and the cylinder operable to determine retracted and projected limit positions of travel of the piston and rod axially in said cylinder, a knife head on one end of said piston rod for movement therewith between retracted and projected positions, knife support means in said knife head axially shiftable therein between inner and outer positions along an axis perpendicular to the axis of the cylinder, pressure fluid actuatable means in the knife head operable to shift said knife support means from said inner position to an outer position, means in said knife head defining a pressure fluid passage communicating between the coaxial pressure fluid passage in said piston rod and said pressure fluid actuatable means in the knife head, means to admit pressure fluid to the cylinder to actuate said piston from said retracted position to said projected limit position, means in the piston rod adjacent the other end thereof defining a pressure fluid inlet passage therein having an inner opening communicating with the coaxial pressure fluid passage in said piston rod and an outer opening for communication with the cylinder interior, the outer opening of said pressure fluid inlet passage being disposed axially in the piston rod so that said outer opening is normally closed by the cylinder in the intermediate and retracted positions of the piston rod and is open and in communication with the cylinder interior only in the projected limit position, and means in the piston rod defining a vent passage having an inner opening communicating with said coaxial fluid passage therein and an outer opening for communication with the external atmosphere, said vent passage being disposed axially in said piston rod and spaced with respect to the pressure fluid inlet opening therein so that the vent outer opening is closed by the cylinder in the projected limit position of the piston rod and is open to the atmosphere in the intermediate and retracted limit positions of said piston rod, whereby pressure fluid can flow from said cylinder to the knife head to axially shift the knife support from said inner position only in the projected limit position of the piston rod and the knife head is vented to atmosphere in said intermediate and retracted positions of the piston rod.

2. A pressure fluid actuated knife holder as claimed in claim 1 comprising means operable to return the piston and piston rod together with the knife head from the projected limit position to the retracted limit posi tion upon cut-off of pressure fluid to the cylinder.

3. A pressure fluid actuated knife holder as claimed in claim 2 wherein the means for returning the piston and piston rod from the projected limit position to the retracted limit position comprises an expansion coil spring circumscribing the piston rod.

4. A pressure fluid actuated knife holder as claimed in claim 1 comprising means operable to return the knife support means to the inner position thereof in the knife head upon venting pressure fluid from the latter.

5. A pressure fluid actuated knife holder as claimed in claim 4 wherein the means for returning the knife support means to the inner position comprises a plurality of expansion coil springs acting between the knife support means and an adjacent portion of the knife head.

6. A pressure fluid actuated knife holder as claimed in claim 1 comprising a circular knife journaled in the knife mounting means for rotation about an axis perpendicular to the axis of the cylinder, said knife having a circumferential cutting edge.

7. A pressure fluid actuated knife holder as claimed in claim 6 wherein the knife mounting means is constructed and arranged for limited pivotal rocking movement in the knife head about a center located on the rotation axis of the knife to permit limited angular deflection of said knife from said axis.

8. A pressure fluid actuated knife holder as claimed in claim 6 wherein the piston rod includes adjustable means operable to determine the projected limit position of the piston and piston rod with respect to the cyl inder and thereby predeterminedly set the projected limit position of the cutting edge of the circular knife.

9. A pressure fluid actuated knife holder as claimed in claim 8 wherein the adjustable means to determine the projected limit position of the piston and piston rod comprises an adjustment member threaded on a portion of the piston rod at the opposite side of the piston from said knife head and manually adjustable on said piston rod.

10. A pressure fluid actuated knife holder as claimed in claim 9 wherein the pressure fluid inlet passage from the cylinder interior to the coaxial pressure fluid passage in the piston rod is in the adjustment member.

11. A pressure fluid actuated knife holder as claimed in'claim 9 wherein the vent passage between the coaxial fluid passage in the piston rod and the external atmosphere is in the adjustment member.

12. A pressure fluid actuated knife holder as claimed in claim 10 wherein the vent passage between the coaxial fluid passage in the piston rod and the external atmosphere is also in the adjustment member.

13. A pressure fluid actuated knife holder as claimed in claim 7 wherein the limited pivotal rocking movement of the knife mounting means is provided by a peripheral surface thereon of arcuate spherical shape having a radius described from the center of pivotal rocking movement of said knife mounting means.

14. A pressure fluid actuated knife holder as claimed in claim 9 wherein the intercooperating means operable to determine the retracted and projected limit positions of the piston rod axially in said cylinder comprises axially spaced means on the adjustment member disposed for cooperative engagement with the cylinder.

15. A pressure fluid actuated knife holder as claimed in claim 2 comprising means operable to return the knife support means to the inner position thereof in the knife head upon venting pressure fluid from the latter.

16. A pressure fluid actuated knife holder as claimed in claim wherein the knife mounting means is constructed and arranged for limited pivotal rocking movement in the knife head about a center located on the rotation axis of the knife to permit limited angular deflection of said knife from said axis.

17. A pressure fluid actuated knife holder as claimed in claim 15 wherein the adjustable means to determine the projected limit position of the piston and piston rod comprises an adjustment member threaded on a portion of the piston rod at the opposite side of the piston from said knife head and manually adjustable on said piston rod.

18. A pressure fluid actuated knife holder as claimed in claim 15 wherein the vent passage between the coaxial fluid possage in the piston rod and the external atmosphere is also in the adjustment member.

19. A pressure fluid actuated knife holder as claimed in claim 16 wherein the vent passage between the coaxial fluid passage in the piston rod and the external atmosphere is also in the adjustment member.

20. A pressure fluid actuated knife holder as claimed in claim 19 wherein the limited pivotal rocking movement of the knife mounting means is provided by a peripheral surface thereon of arcuate spherical shape having a radius described from the center of pivotal rocking movement of said knife mounting means.

21. A pressure fluid actuated knife holder as claimed in claim 20 wherein the intercooperating means operable to determine the retracted and projected limit positions of the piston rod axially in said cylinder comprises axially spaced means on the adjustment member disposed for cooperative engagement with the cylinder.

Claims

1. A pressure fluid actuated knife holder comprising a cylinder, a piston rod extending axially through said cylinder beyond the ends thereof and having a pressure fluid passage extending coaxially therein, a piston in the cylinder secured on said piston rod, intercooperating means on the piston rod and the cylinder operable to determine retracted and projected limit positions of travel of the piston and rod axially in said cylinder, a knife head on one end of said piston rod for movement therewith between retracted and projected positions, knife support means in said knife head axially shiftable therein between inner and outer positions along an axis perpendicular to the axis of the cylinder, pressure fluid actuatable means in the knife head operable to shift said knife support means from said inner position to an outer position, means in said knife head defining a pressure fluid passage communicating between the coaxial pressure fluid passage in said piston rod and said pressure fluid actuatable means in the knife head, means to admit pressure fluid to the cylinder to actuate said piston from said retracted position to said projected limit position, means in the piston rod adjacent the other end thereof defining a pressure fluid inlet passage therein having an inner opening communicating with the coaxial pressure fluid passage in said piston rod and an outer opening for communication with the cylinder interior, the outer opening of said pressure fluid inlet passage being disposed axially in the piston rod so that said outer opening is normally closed by the cylinder in the intermediate and retracted positions of the piston rod and is open and in communication with the cylinder interior only in the projected limit position, and means in the piston rod defining a vent passage having an inner opening communicating with said coaxial fluid passage therein and an outer opening for communication with the external atmosphere, said vent passage being disposed axially in said piston rod and spaced with respect to the pressure fluid inlet opening therein so that the vent outer opening is closed by the cylinder in the projected limit position of the piston rod and is open to the atmosphere in the intermediate and retracted limit positions of said piston rod, whereby pressure fluid can flow from said cylinder to the knife head to axially shift the knife support from said inner position only in the projected limit position of the piston rod and the knife head is vented to atmosphere in said intermediate and retracted positions of the piston rod.

2. A pressure fluid actuated knife holder as claimed in claim 1 comprising means operable to return the piston and piston rod together with the knife head from the projected limit position to the retracted limit position upon cut-off of pressure fluid to the cylinder.

8. A pressure fluid actuated knife holder as claimed in claim 6 wherein the piston rod includes adjustable means operable to determine the projected limit position of the piston and piston rod with respect to the cylinder and thereby predeterminedly set the projected limit position of the cutting edge of the circular knife.

11. A pressure fluid actuated knife holder as claimed in claim 9 wherein the vent passage between the coaxial fluid passage in the piston rod and the external atmosphere is in the adjustment member.

16. A pressure fluid actuated knife holder as claimed in claim 15 wherein the knife mounting means is constructed and arranged for limited pivotal rocking movement in the knife head about a center located on the rotation axis of the knife to permit limited angular deflection of said knife from said axis.